A wireless network is a system whose devices communicate each other through radio waves, without using cables. The basic element of the network is called a node, and the root node is typically referred to as the gateway. This gateway is the main interface between the wireless network and an external system, which is typically an existing wired fire system handled by a panel.
The gateway is in charge of translating the messages traveling between wired (panel) and wireless (nodes) domains in order to make the wireless nodes “attached” to the gateway and visible to the panel of the wired network as if they would be physically connected to the wired network. All wireless devices except the gateway are battery powered. Therefore, the current consumption will preferably be kept to the lowest possible level in order to maximize devices' lifetimes.
A node typically consumes most of the power while communicating with other nodes; the most power saving configuration (topology) is the star, as illustrated in FIG. 1, in which the number of links of every single node is limited to the minimum required to meet network constraints.
The star configuration can only be used if the communications link (both physical distance and obstacles) between nodes and the gateway is good enough to allow for a direct link between every single node and the gateway. Moreover, it's necessary that all nodes are able to establish a good enough link with at least one other node in order to guarantee that a secondary path is always available. In most cases, not all nodes are able to communicate directly with the gateway. Therefore, they communicate with the node closest to them, which, in turn, will forward the received information.